Making granulated explosives



A ril 4, 1944. w. o. S NELLING MAKING GRANULATED EXPLOSIVE Filed Feb. 11, 1942 INVENTOIQ. hall?! JI /lug BY HTRWPNE') Patented Apr. 4, i944 STA OFFICE MAKING GRANULATED EXPLO SIVES Walter 0. Snelling, Allentown, Pa, assignor to Trojan Powder Company, a corporation of New York 1 Claims.

This invention relates to a method of makin a granular mixed explosive and particularly to the cocrystallizing of trinitrotoluene and pentaerythritol tetranitrate in an economical and convenient manner, so as to produce granules that are of substantially uniform composition throughout and free from objectionable proportions of either excessively fine or coarse material.

The formation of granules of cocrystallized trinitrotoluene and pentaerythritol tetranitrate is desirable in increasing the intimacy of association of the two explosives, eliminating variations in overall density, and decreasing the formation of objectionable amounts of fine and therefore oversensitive material.

The cocrystallized mixture of these two explosives is sometimes known as Pentolite." Because of its great importance and the special conditions required for its manufacture, the invention will be illustrated in detail by description in connection with the making of Pentolite granules of desired size and thoroughness of blending of the pentaerythritol tetranitrate with trinitrotoluene, the term blending including coating of one material with the other or association of other nature that causes the formation of granules of approximately the same composition throughout.

In making a blended explosive such as Pentolite, it is not satisfactory to effect perfect blending in a large part of the resulting material but imperfect blending in even a minute proportion of the mass. The presence of any particles or only portions of particles of widely varying composition substantially decreases the constancy of the properties which is desired and which is obtained by intimate blending of the two explosives. It is essential, therefore, that all of the granules be of the proper nature and that there be no nonuniform portions of material in which, for instance, the pentaerythritol tetranitrate may be protected with the trinitrotoluene in one part of the granule and left uncoated or unblended in appreciable amount in another part of the material.

The present invention provides a convenient method of making granules of the required uniformity and size.

Briefly stated, the invention comprises forming a solution of the explosive compounds to be cocrystallized in a solvent that is soluble in water,

introducing the said solution through one or more small orifices into water or a water-containing precipitating liquid that is being vigorously stirred or otherwise moved rapidly past the point of introduction of the solution, separating the resulting granules of the solid explosive mixture from the remaining liquid, and drying the separated granules.

In this process, the aqueous liquid which is rapidly moved by agitation or otherwise prevents accumulation of the introduced solution into large masses and divides the solution into small droplets that are suspended in the water in discrete relationship to each other. The aqueous liquid then converts the explosive compounds from dissolved to solid condition.

The mechanism of this conversion is largely entrance of water into the minute droplets of solution so as to dilute the solvent and leaching of solvent away from the explosive compounds in the droplets. Whatever may be the predominating effect, it is described herein for convenience as removal of solvent from the droplets.

Because the dilution of the solvent or the removal of solvent by extraction from the very fine droplets of the solution is practically immediate,

the explosive compounds do not have time for segregation, each by itself, as they are converted to solid form; the result is the production of granules that are substantially uniform in overall composition and without objectionable local overconcentration of either explosive in any part of a given granule,

Furthermore, the granules made as described are relatively uniform in size and free from obiectionably fine dust-like material or from coarse over-size masses. In a typical run, the granules made were found by test to be of such size that more than 90% by. weight passed through an 18 mesh screenand were retained on a mesh screen.

Suitable apparatus for use in the practice of the invention is illustrated in the drawing to which reference is made.

Figs. 1 to 5 are sectional views of such equipment, Fig. 2 being a perspective view shown only partly in section.

There are shown a container l0 holding a liquid l2, an agitator It with conventional drive (not shown) for stirring the liquid vigorously, and a spray member for delivering to liquid l2 the solution l6 of the explosive compounds to be cocrystallized.

The orifices in the spray member are of capillary fineness, as, for example, of diameter 0.015 to 0.05 inch. The sizes of the orifices may be varied somewhat, however, the larger the orifice within limits, the larger the average size of granules produced. The diameter of the orifices should not be so large that the mass of solid explosive from single droplets of the solution, after delivery from the orifices and suspension in water, exceeds the allowable mass of the finished granule of the explosive. The orifices should not be so fine, on the other hand, as to become plugged with material. I

The spray member which is preferred is that shown at l8 in Fig. 1. It includes a spray head submerged in the liquid l2, pointing downwardly and provided on its face with a large number of the orifices.

Other means of introducing the solution of th explosives may be substituted for this member as, for example, a tube or tubes 20 provided each with one or more orifices or an inlet pipe 22 which is formed at its lower submerged end into approximately a ring shape and provided with orifices. These modifications of the apparatus are shown in Figs. 2 and 3. In any case, the orifices are of size stated above.

In a further modification of the apparatus shown in Fig. 4 the solution .of the explosive compounds to be cocrystallized is passed through capillary orifices in one or more tubes 24, the orifices in these tubes being disposed above the level of the precipitating liquid i 2 so that the small streams which pass through the orifices fall through an air space and are thus caused to be reduced further in diameteror formed into drops before striking the precipitating bath.

The containers l shown in Figures 1 to 4 are provided with outlets 34 near the bottoms of those tanks, these outlets being constructed suitably of non-sparking material as. for example, of wood, plastic, or hard rubber pipe or the like with valves of similar material.

A further' modification of the apparatus is shown in Fig. 5. Here the apparatus resembles somewhat the common blast lamp. The solution l6 of the explosive compounds is passed through the inner pipe 26 and the precipitating liquid I2 is passed rapidly in the same direction through the jacket 30 and around the orifice in the inner pipe. At the nozzle 32 of the apparatus there is thus formed a mixture, usually a spray, of intermingled very fine droplets of the solution of the explosive compounds and the precipitating liquid I2. The mixture so formed'is delivered to a filter, the liquid separated, and the granules remaining on the filter are dried, as will be described later.

In all embodiments of the invention, the pentaery'thritol tetranitrate and the trinitrotoluene to be cocrystallized are first dissolved in the selected solvent in a suitable container (not shown) and then passed in any convenient manner, under at least moderate pressure or liquid head, through the member provided with an orifice or orifices into the precipitatin liquid I 2. Suitably I place the solution in a conventional pressure tank and then, by air pressure upon the solution, force it through one of the members I8, 20, 22, 24, or 26 in the assembly shown in the various figures.

The introduction into the liquid l2 of the solution l6 of explosives that are to be cocrystallized is continued until there is formed a rather thick suspension of the resulting granules of cocrystallized material (represented by dots in the several figures) in the precipitating liquid 12. The introduction of the solution I6 is then discontinued, the valve in outlet 34 is opened, and the mixture of granules and adhering liquid is delivered to a separator (not shown).

A suitable separator is a standard filter or basket-type centrifuge, a simple vacuum filter of the large or all proportions with water.

stoneware jar type being satisfactory. After the liquid is separated as nearly completely as feasible in the separator, the remaining granules are washed with water so as to remove largely the remaining solvent used in making the original solution of the explosives.

The washed granules are then dried at a temperature below their melting point, say in trays, at about C., temperatures between atmospheric and the melting point of the cocrystallized material being permissible. Temperatures of about 60 to C., are preferred; such temperatures give a relatively high rate of drying and at the same time avoid danger of melting the material.

The liquid separated as described is sent to conventional distillation or fractionation equipment for recovery of the solvent for reuse in dissolving a fresh lot of pentaerythritol tetranitrate and trinitrotoluene.

To clean out the line and orifices used for introducing the solution of the explosives into the precipitating liquid, there may be used, with any of the members I8, 20, 22, 24, or 26 a connection such as shown at 36 in Fig. 2. This connection is a pipe provided with suitable fittings and valve for introducing solvent to dissolve any solidified explosive material that may have been deposited in the said line or orifices. When such connection is used, there is employed also a valve 38 for preventing flow of the solvent in the direction of the fresh solution of the explosive compounds.

Such a connection is desirable also for use in filling the spray member initially with the solvent. alone, which is followed through, at the start of a run, by the solution I6 so that the solution never strikes the precipitating liquid until after the solution passes through the orifice or orifices.

The solvent used initially to dissolve the explosives to form the solution l6 should be either a single liquid or a mixture of liquids, a good solvent for and chemically inert to the mixed explosives, and soluble and preferably miscible in A suitable solvent is acetone. For best results in forming a solution that does not plug the orifices, the

acetone should contain not substantially more than 12 per cent 0! water.

In place of acetone, there may be used other solvent that meets the general requirements stated as, for example, organic liquids such as methyl ethyl ketone and a mixture of equal partsof acetone with methyl or ethyl alcohol.

Depending upon the particular solvent used, proportions of the several materials are adjusted to meet the following requirements: The trinitrotoluene and pentaerythritol tetranitrate must dissolve completely in the solvent at the temperature at which it is'delivered to the precipitating liquid l2 and the latter must dissolve the solvent and cause precipitation of practically all ofthe trinitrotoluene and pentaerythritol tetranitrate. a

In order to save solvent and obtain the most economical production of the granules, the concentration of the explosives in the solvent should be large and near the saturation point. Also, the solvent may be warmed to some temperature moderately or considerably above atmospheric but below the boiling point of the solvent at the pressure acting upon it, in order to increase the proportion of the explosives that may be dissolved andreduce the viscosity of the solution,

- for a given concentration oi! dissolved explosives,

tone at a temperature of about 40 to 55 C. in

which case three parts of acetone are satisfactory for dissolving one part each of trinitrotoluene and pentaerythritol tetranitrate. When I have used acetone at atmospheric temperatures, then the proportions employed are suitably about four parts or slightly more of acetone to one part each of the said explosives.

The precipitating liquid ii at the start of an operation is suitably water. As the operation proceeds, the liquid becomes a mixture of water with a minor proportion of the solvent initially used.

The proportion of water used, for the suspension of the solution of the explosives as minute droplets and subsequent conversion. of the explosives to solid form, should be adequate to give a good suspension of the droplets oi! the solution that are formed in the agitated water and maintain the droplets in discrete relationship toieach other. The proportion oi water used must always be in excess of the acetone used. Otherwise, there is obtained a system with two liquid phases. At

the same time, the proportion of water should not be so excessively large as to introduce unnecessary cost oi. recovering the solvent, as by distillation from its solution in water. I have used to advantage about '7 to 15 parts 01' water to 3 to 4 parts of the acetone solution containing 1 part each of trinitrotoluene and pentaerythritol tetranitrate, proportions here and elsewhere herein being expressed as parts by weight.

In any case, the temperature oi the water should be not substantially above about 57? 0., as above that temperature there is objectionable increase in size of the granules of explosives produced. Temperatures of the water of 20 to 35' are preferred, although the process is operative .when the temperatureis within the range of about to 57 C. Temperatures within this range are below the melting point of the explosives separately and also of the resulting mixed explosives which, as indicated above, are not subject to melting at temperatures as high as 70 C.

Proceeding as. described, I have made cocrystallized granules of the two explosives that are so nearly uniform in size that it is not necessary to screen the product to remove either excessively fine or over-size material. Furthermore, the

granules so prepared are "of consistent composition throughout.

What I claim isf 1. The method of making a granular mixture of the explosives trinitrotoluene and pentaerythritol tetranitrate which comprisesiorming a solution of the explosives in a solvent, delivering the solution through a small orifice oi capillary flneness'into a water-containing precipitating liquid that is a non-solvent for the explosives but that dissolves the said solvent and is maintained at a temperature below the-.melting point of the mixed explosives and of each 01 them,

vigorously moving the said liquid as the solution is delivered thereinto so as to form the solution into fine droplets, the explosives b'eing thus con-' verted to solid granular condition, and separating the resulting granules from the liquid present.

It will be understood also that it is intended to cover all changes and modifications of the example of the inventionherein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

, 2. The method described in claim 1, the said solvent being a volatile organic liquid and the said solution as delivered into the water bein maintained at a temperature below the .boiling point oi the solvent therein and not substantially above 57 C.

3. The method described in claim 1, the said solvent including a volatile organic compound, the solution as delivered into the said liquid being-maintained at a temperature below the boiling point or the solvent, the orifice being of diameter about 0.015 to 0.05 inch, and the said granules as separated from the said liquid being at a temperature below the melting point of any explosive material present.

4. The method described in claim 1, the said solvent being an organic liquid containing a water-soluble ketone. Y

5. The method described in claim 1, the said solvent being an organic liquid consisting principally of acetone, and the precipitating liquid being used in excess of the amount of acetone and at a temperature not substantially above C.

6. The method described in claim 1, the said solvent being an organic liquid consisting principally of acetone and the materials being used in approximately the following proportions: 1

part of each 01' the explosives, 3 to 4 parts of acetone, and water, as the precipitating liquid, at least 7 parts.

'1. The method-oi making a granular mixture of explosives which comprises i'orming a solution or trinitrotoluene and pentaerythritol tetranitrate in a liquid water-soluble organic solvent for the explosives, delivering the solution as a stream through a smal1 orifice, forcing a stream of water rapidly from aiacket around the said orifice so that the streams oi! the said solution and water move inv the same general direction and intermingle, there being formed a suspension or the said solution in the form of minute droplets in the water which removes solvent from the droplets causing solidification in granular form of the explosives present.

. WALTER 0. SNEILING. 

